﻿using System;
using System.Text;
using System.Security.Cryptography;
using System.IO;
/*************************************************************************************
 * CLR版本：  4.0.30319.296
 * 类 名 称： EncryptAString
 * 文 件 名： EncryptAString
 * 创建时间： 2012-12-14 20:38:34
 * 说   明：  加/解密
 * 修改记录：
 *************************************************************************************/

namespace Filter
{
    public class EncryptAString
    {
        //加/解密字符串的密钥
        public static readonly string objKey = "qroihlgz";
        public static readonly string objIV = "cfs545";

        /// <summary>
        /// 加密字符串
        /// </summary>
        /// <param name="pToEncrypt"></param>
        /// <param name="sKey"></param>
        /// <returns></returns>
        public static string EncryptStr(string pToEncrypt, string sKey)
        {
            return EncryptStr(pToEncrypt, sKey, sKey);
        }

        /// <summary>
        /// 加密字符串
        /// </summary>
        /// <param name="pToEncrypt"></param>
        /// <param name="sKey"></param>
        /// <returns></returns>
        public static string EncryptStr(string pToEncrypt, string sKey, string sIV)
        {
            //加密结果和明文长度问题
            //1-7=16位
            //8-15=32位
            //16-23=48位
            if (pToEncrypt.Length == 0)
                return "";

            //访问数据加密标准(DES)算法的加密服务提供程序 (CSP) 版本的包装对象
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);　//建立加密对象的密钥和偏移量
            des.IV = ASCIIEncoding.ASCII.GetBytes(sIV);　 //原文使用ASCIIEncoding.ASCII方法的GetBytes方法

            byte[] inputByteArray = Encoding.Default.GetBytes(pToEncrypt);//把字符串放到byte数组中

            MemoryStream ms = new MemoryStream();//创建其支持存储区为内存的流　
            //定义将数据流链接到加密转换的流
            CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            //上面已经完成了把加密后的结果放到内存中去

            StringBuilder ret = new StringBuilder();
            foreach (byte b in ms.ToArray())
            {
                ret.AppendFormat("{0:X2}", b);
            }
            ret.ToString();
            return ret.ToString();
        }

        /// <summary>
        /// DEC 解密过程
        /// </summary>
        public static string DecryptStr(string pToDecrypt, string sKey)
        {
            return DecryptStr(pToDecrypt, sKey, sKey);
        }

        /// <summary>
        /// DEC 解密过程
        /// </summary>
        public static string DecryptStr(string pToDecrypt, string sKey, string sIV)
        {
            if (pToDecrypt.Length == 0)
                return "";

            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            byte[] inputByteArray = new byte[pToDecrypt.Length / 2];
            for (int x = 0; x < pToDecrypt.Length / 2; x++)
            {
                int i = (Convert.ToInt32(pToDecrypt.Substring(x * 2, 2), 16));
                inputByteArray[x] = (byte)i;
            }

            des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);　//建立加密对象的密钥和偏移量，此值重要，不能修改
            des.IV = ASCIIEncoding.ASCII.GetBytes(sIV);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);

            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();

            //建立StringBuild对象，createDecrypt使用的是流对象，必须把解密后的文本变成流对象
            StringBuilder ret = new StringBuilder();

            return System.Text.Encoding.Default.GetString(ms.ToArray());
        }
    }
}
